Preparation And Photocatalytic Study Of Ag₃PO₄@Benzoxazine Soft Gel Composites

In nature, a lot of chemical reactions in plants can be driven by sunlight. We human beings have long aspired to synthesize molecules in the same manner that plants do. This is a green development path. Photocatalysis have been studied widely in decomposing water hydrogen, degradating organic pollutants in water and catalyzing organic reactions. However, It is still one of the biggest challenges in synthesis of visible light catalyst with best catalytic performance and lowest price by simple preparation process.Based on the molecular self-assembly of benzoxazine monomer attached onto the surface of the Ag3PO4 nanoparticles, a new type Ag3PO4 nanocrystalline@benzoxazine soft gel core-shell composites(hereinafter referred to as the Ag3PO4@BSG) were created. The photocatalytic performance of the Ag3PO4@BSG composites was evaluated by degradation of rhodamine B and methyl orange. The preparation conditions and use conditions were also tested to study the affect on the performance of Ag3PO4@BSG composites. The formation mechanism of Ag3PO4@BSG composites and relationship between performance and structures were further studied.The Ag3PO4 nanoparticles had been successfully synthesized by Ag NO3 and Na2HPO4·12H2O through a simple liquid precipitation method. Benzoxazine monomer was prepared with melamine, phenol and formaldehyde by Mannich reaction. Then, The Ag3PO4@BSG composites were obtained through molecular self-assembly of Ag3PO4 nanoparticles with benzoxazine monomer in toluene dispersion medium. The photocatalytic properties of the Ag3PO4@BSG composites were evaluated using the degradation of rhodamine B and methyl orange under Xe lamp irradiation. The photocatalysts of the Ag3PO4@BSG composites were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectrometer, fourier transform infrared spectrometer. The results indicate that the nanocomposites exhibit a high visible light photocatalytic activity, and its photocatalytic stability is much higher than the bare Ag3PO4 nanoparticles. The benzoxazine monomers are attached to the surface of Ag3PO4 nanoparticles by coordination interaction between the amino group of the benzoxazine and Ag+ ions on the surface of Ag3PO4, and the soft gel shell is formed via the interaction of hydrogen bonds between the benzoxazine monomers. The high photocatalytic stability of Ag3PO4@BSG nanocomposites mainly originates from the silver amine complex ion formed in the interface between the core and the shell. The silver amine complex ion can protect the Ag3PO4 from photoreduction(Ag+ + e-→Ag), and the photoexcited electron–holes in the nanocomposites are separated efficiently. In addition, the encapsulation of Ag3PO4 core with benzoxazine soft gel shell effectively inhibit Ag3PO4 from dissolution.The integration of soft gels widely existed in plant tissue can provide a new way to create a high efficiency, cheap and stable performance of Ag3PO4@BSG photocatalysts. Continuing research on the physico-chemical properties of the soft gel may promote the development of artificial systems that can mimic natural photosynthesis to synthesize molecules in the same manner plants.